The Radical Anions of 5,5′- and 6,6′-Biazulenyl

ESR. and, in part, ENDOR. studies are reported on the radical anions of 5,5′‐and 6,6′‐biazulenyl (1 and 2, resp.), as well as on their 1, 1′, 3, 3′‐tetradeuterioderivatives (1‐d4 and 2‐d4). The reduction processes of 1 and 2 leading to these radical anions (\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\ominus \atop \dot{}}$\end{document}) and the dianions ( ) have been investigated by polarography and cyclic voltammetry. The half‐wave reduction potential of 1 and the π‐spin distribution in \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\ominus \atop \dot{}}$\end{document} are consistent with the model of two weakly interacting azulene π‐systems, whereas the analogous findings for 2 and \documentclass{article}\pagestyle{empty}\begin{document}$ 2^{\ominus \atop \dot{}}$\end{document} point to a strong interaction between two such systems. This difference can be traced to the distinct inequality ∥c65 ∥ « ∥ c66 ∥ in the LCAO coefficients c6μ at the centres μ=5 and 6 for the LUMO Ψ6 of azulene.